1. Field of the Invention
The present invention generally relates to robots. More particularly, the present invention relates to compensating for differences in the spacing between a plurality of robot blades and the spacing between the different objects with which the different robot blades interact.
2. Background of the Related Art
Robots are used to transfer substrates, e.g. wafers, LED displays, etc. between different process cells, transfer cells, spin-rinse-dry (SRD) cells, integrated bevel clean (IBC) cells, metrology cells that measure and/or inspect substrates, and other known cells adapted to perform semiconductor processes. In semiconductor processes, multiple process cells frequently are combined to form a single cluster tool. Robots are typically used to transfer substrates between the different process cells in a cluster tool. Examples of processes that are performed in certain cells in cluster tools include chemical vapor deposition (CVD), physical vapor deposition (PVD), and electro-chemical plating (ECP).
Robots typically load substrates into, and unload substrates from, process cells using substrate holder systems. The substrate holder systems transfer the substrates between the loading or unloading position and the processing position. Multiple substrates are often transferred simultaneously between different process cells, in which each cell contains one of the multiple substrates, to increase processing throughput. Multiple substrates may even undergo identical processing in different process cells simultaneously. Multiple blade robots are therefore configured to provide for simultaneous transfer of pairs of substrates between pairs of process cells. A first robot blade positions a substrate in, or removes a substrate from, a first process cell, concurrently as a second robot blade or multiple blades, positions a second substrate in, or removes a substrate from, a second process cell. An example of such multiple blade robots is provided in U.S. Pat. No. 5,838,121 that issued Nov. 17, 1998 to Fairbaim et al., and entitled xe2x80x9cDUAL BLADE ROBOTxe2x80x9d (Incorporated herein by reference).
Not all pairs of process cells in a cluster tool are spaced the same distance apart. During mounting of different groups of process cells in one cluster tool, the spacing between adjacent cells may vary by a fraction of an inch. A robot with multiple robot blades that is spaced to insert/remove substrates from an ECP cell therefore may not have the correct spacing to insert/remove substrates from a CVD cell, for example.
It is difficult to match the distance between the pairs of robot blades, that carry the substrates, to the distance between the pairs of cells or substrate holder assemblies. This lack of matching causes difficulty in loading the substrates into, or unloading the substrates out of, the cells. An inconsistency in spacing of a quarter of an inch between pairs of process cells is common. Such inconsistencies can be caused by unequal spacing between different pairs of cells in a cluster tool, the normal dimensional tolerances on the robots and processing equipment, and/or thermal expansion differences of the mounting between pairs of cells considering that some of the cells operate at different temperatures.
Therefore, there remains a need for a cluster tool configuration involving multiple blade robots that can transfer pairs of substrates between multiple process cell pairs, and that can also provide a fine alignment to compensate for inconsistent spacing between these process cells.
The present invention generally provides a robot system apparatus and an associated method. The robot system comprises a multiple blade robot and a compensating device. The multiple blade robot includes at least one set of robot blades. The compensating device adjusts for differences in spacing between the set of robot blades and spacing between two or more cells. In different embodiments, the compensating device may be coupled to one or more of the process cells, one or more of the substrate holder assemblies, or one or more of the robot blades.